This invention relates to motion picture film projection and, more particularly, it concerns an improved feed shuttle mechanism for incrementally advancing a film strip to present successive image frames thereon to a framing window or the like for the projection of light through the film to an optical system for viewing.
The projection for viewing of motion picture film strips requires that each successive image frame on the film strip be presented in a momentarily still position in registry with a framing aperture through which light is transmitted to present the image on a screen or the like. For this reason, the film is provided with a series of equally spaced feed apertures along at least one marginal edge to be engaged by a feed shuttle claw capable of movement normal to the film strip to engage the spaced apertures, parallel to the plane of the strip to advance the strip in an increment of distance equal to the length of one frame, withdraw from the apertures and return for successive feed cycles. Because of the speeds at which such a shuttle is operated, the compound nature of the feed shuttle claw movement, together with the requirements for precision and synchronization with other projector components, the feed shuttle represents perhaps the most sophisticated mechanical organization in a motion picture projector. As a result, numerous feed shuttle designs have evolved out of the continuing effort to simplify feed shuttle mechanisms while retaining or improving upon the operational characteristics thereof.
One such feed shuttle mechanism is shown and described in copending U.S. application Ser. No. 756,330, now abandoned, which is assigned to the assignee of the present application. In the above-cited application, a film engaging claw of a shuttle is supported in lateral cantilevered fashion centrally along the length of an elongated, transversely arcuate body member adapted to be driven by a single compound cam for both reciprocation in a longitudinal direction parallel to the direction of the film strip advance and rotationally such that the laterally extending claw undergoes the appropriate vertical movement for engaging entry and disengaging withdrawal of successive film strip feed apertures. The shuttle is exclusively supported by a pair of longitudinally spaced springs adapted to retain the arcuate body against quadrant bearing blocks located at opposite ends of the body in the vicinity of the springs as well as against the surfaces of the actuating cam. The lateral extension of the claw portion contributes not only to the required compound movement of the shuttle, but also enables the shuttle to be mounted along the exterior structure adapted to receive a cassette in which the film strip is contained.